ES2565234T3 - Fracture fixation system - Google Patents

Abstract

A fixing system designed to hold bone pieces (4, 5) together, said fixing system comprising: a fixing element (16) designed to be attached to a first bone piece (4), a plate (11) comprising a spherical hole (15), and a bearing (17) to hold the fixing element (16) in an angular position adjusted within the hole (15) of the plate (11), said plate being designed to be held in a second bone piece (5) and to thereby hold the bone pieces (4, 5) together, said bearing (17) having an outer surface designed to rotate within the hole (15) of said plate, said bearing ( 17) a hole (21) into which the fixing element (16) is inserted and can be adjusted angularly by turning the bearing (17) into the hole (15) of the plate (11), in which the diameter of the said hole decreases from a wider diameter in a plane that passes through a equatorial zone of the hole to narrower diameters in respective planes along the upper and lower surfaces of the plate, and said bearing (17) is provided with a first end part having a spherical surface, a second end part having a spherical surface, and groove means (32) therein to allow radial expansion of the bearing when the fixing element (16) is advanced within the bore (21) of the bearing (17), in which the groove means they are constructed and placed in the bearing to hold the bearing on the plate, and in which said groove means comprise a plurality of grooves (32) extending from the first end part of the bearing partially along the length of the bearing up to a position located more than half the length of the bearing, characterized in that, the grooves define lever-shaped petals (35) around said bearing, the element comprising fixing part a part with a diameter that is greater than a diameter of a part of the hole comprising the lever-shaped petals (35), such that the advance of the bone fixing element (16) towards said part inside of said bore (21) causes the tips of the lever-shaped petals (35) to move outwardly to cause the spherical surface located in the first final part of the bearing (17) to rest against a spherical bore surface on a first side of the equatorial zone, while the spherical surface located in the second final part of the bearing (17) rests against a spherical surface of the hole on an opposite side of the equatorial zone to develop a non-uniform distribution of force between the bearing and the plate that resists the moments applied to the bone fragment migration fixation element when the fracture fixation system is holding the bone pieces (4, 5) as with each other.

Description

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DESCRIPTION

Fracture fixation system

The invention is related to a fracture fixation system in which a fixation element is held in a bone fragment and locked in an adjustable angle position in a plate attached to stable bone.

The system comprises a bearing that is located on the plate and that locks the post (the fixing device) into the plate as the post is inserted into the bearing.

A method for fastening a fixing device in an angled position in a bearing, which is also held in a hole in a plate, is also described.

Fracture fixation near an articular surface is often performed with devices, such as a support plate, to support the articular surface preventing it from moving. These devices share several common features: almost all of them are manufactured as a plate that has fixation of the central fragment with one or more bone screws and that provides fixation of the periarticular fragment with one or more support teeth, posts, or interlocked screws.

Such a device is shown in the published US Patent Application. No. 20030105461 (Putnam) and comprises a plate with fixed teeth extending at an angle to the plane of the plate. These teeth are contiguous to the plaque and extend forming a fixed angle. A disadvantage of this construction is that the teeth are located in fixed positions and the surgeon must implant all of them. Often the geometry of the fracture is such that the teeth are not optimally positioned and can enter a fracture point or can protrude into the joint.

Another device includes plates that have screws or fixed posts that are threaded into a threaded hole in the plate. They are also known, as shown in US Pat. No. 6,358,250 to Orbay, plates in which posts or screws are inserted at varying angles. These constructions require that the head of the post or of the screw have sufficient grip of its thread fillets in the thread fillets of the plate hole; This requires that the plate be thick enough to allow an adequate number of thread fillets for fixing the post or screw. In addition, these plates require that the post or screw be inserted at a predefined angle.

An additional device is shown in US Pat. No. 6,364,882 to Orbay and in the published US Patent Application. No. 2002/0143338, in which the post or screw is provided with a partial spherical head so that it can be placed on the plate at a variable angle, and after that it can be fastened with a fixing screw. The spherical head is provided with grooves to facilitate its expansion inside the hole when it is secured by the fixing screw. Although this construction allows greater flexibility to insert the post at a variable angle, it requires an even greater plate thickness to compensate for the thickness of the post head or the screw inside the plate hole while providing a sufficient number of fillets of thread so that the fixing screw grips them. In addition, since the fixing screw only compresses the head of the post or of the screw in a rather small surface area, the friction forces generated are relatively small, so there is a risk of improper fixing of the post or of the screw and of the rear postoperative angulation and loss of reduction. In addition, this system is cumbersome to use because it is necessary for the surgeon to manipulate a small fixing screw behind the head of the post or screw, resulting in greater difficulty in the surgical technique. Finally, because the head of the fixing post is grooved, it creates an area of considerable weakness in the areas where the rod of the post connects with the grooved head. This is subjected to a considerable moment and is prone to breakage.

In US Pat. No. 5,954,722 (Bonus) another device is shown, in which a split bushing is engaged in a plate and houses a bone screw that expands the bushing and frictionally engages said bushing in the carriage. Although this configuration is useful for compressing the head of the post to prevent it from receding and exiting, it does not produce a large surface area of contact between the bushing and the hole surface. The bushing is narrow and has a spherical radius that is slightly smaller than that of the hole to allow initial rotation of the bushing inside the hole to orient the screw. As the head of the bone screw expands cylindrically to the bushing, the bushing contact with the surface of the plate hole is mainly restricted to a narrow contact area along a single equatorial plane of the bushing, since the curvature of the bushing along its main axis is more pronounced than that of the hole. Although this configuration generates compression forces on the head of the screw to prevent it from receding and exiting, if forces on the bone fragment generate moments on the post, resistance to moments is limited to the frictional forces generated from this limited plane of contact of the cap along the equatorial zone. The device is intended to be used in the stabilization of multiple vertebrae in the spine and the friction forces are designed to prevent the screws from backing out of the plate, but they are not intended, nor are they sufficient for it, to resist moments imposed on the screws by displacement of an unstable bone fragment of a fracture.

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Another limitation of the device of US Pat. No. 5,954,722 (Bonus) is that the bushing allows variation of the insertion angles within a predefined conical range. However, there are clinical situations in which it is desirable to limit the range of insertion angles mainly along a single plane. For example, in some situations it may be desirable to allow variation along an axis from proximal to distal, but limit variation from side to side so that the post does not penetrate the joint or other important structures.

Another limitation of the device of US Pat. No. 5,954,722 (Bonus) is that the bushing tends to turn on itself as the post head is inserted. Because the size of the bearing is reduced, it becomes increasingly difficult to insert the post completely since the bearing rotates on itself before sufficient expansion has occurred to generate large frictional forces.

U.S. Pat. No. 5,053,036 describes a system with the features of the preamble of claim 1 attached and in which, when the bearing is radially expanded, its outer surface rests against the surface of the plate hole, generating frictional forces to immobilize the bearing and fixing element. This document does not suggest that the expansion of the bearing be asymmetric.

U.S. Pat. No. 4,388,921 describes a system similar to that of US Pat. No. 5,053,035, in which the grooves further define petals that expand asymmetrically, but the hole does not narrow in diameter from an equatorial zone to a plane along the upper surface of the plate.

U.S. Pat. No. 6,030,389 describes a system with the features of the preamble of claim 1 except that the grooves do not extend to a position more than half the length of the bearing. Its fixing element may have a threaded part that meshes with a thread of the bearing bore.

An object of the invention is to provide a fracture fixation system that avoids the problems described above and whereby a reliable and simple fastening of the post or screw to the plate is obtained.

The fixing system comprises an implant based on a concept of providing an intermediate fixing element or bearing between the post or screw and the hole of the plate. In one embodiment the post is threaded into this intermediate element to cause the thread threads of the post to produce expansion or displacement of the intermediate element against the hole in the plate. This intermediate element can be inserted into the hole of the plate before said plate is applied to the bone, so no manipulation of small and cumbersome fixing screws is necessary. In addition, since compression of the intermediate element occurs through the periphery or surface of the plate hole, a greater surface area for compression is obtained, which results in greater resistance to moments. Since the thread fillets are distributed within the intermediate element, the plate does not have to be made excessively thick to allow sufficient grip of thread fillets for fixing. In addition, the construction of the invention allows it to be possible to place the post or screw in a range of angles, either along two independent degrees of freedom (in a variety of conical positions) or by varying mainly along a single degree of freedom (varying along a single plane directed by the shape of the hole and the bearing).

Finally, since the head of the post is not divided with a thin area of connection with the rod of the post, the risk of breaking the post or screw caused by the moments is greatly reduced.

The invention is characterized by the forming of the bearing in such a way that more than one contact zone is produced when the bearing is expanded, which provides greater resistance to the moments applied to the post or screw by the tendency of the bone fragment to move, then of its fixation. By providing more than one contact zone, there is an uneven distribution of radial forces between the bearing and the plate to resist the applied torque in addition to the frictional forces. In addition, certain variations allow the production of a pair of forces, providing greater resistance to the applied moments.

More specifically, the bearing has an outer surface of spherical contour that can be rotated angularly within a spherical bore of the plate, and the bearing is provided with one or more longitudinal grooves extending from a bearing pole partially or completely along the length of the bearing to cause expansion to occur when the post or screw engages inside the bearing, which creates multiple contact areas at the top and bottom of the bearing to improve resistance at applied times over the post or screw through the bone fragment.

Some embodiments of the invention restrict the range of insertion angles to a single plane, or to a limited variation on both sides of a single plane, to improve the resistance to the moments applied to the post at right angles to the plane and also to restrict the possible insertion angles at a predefined range.

Some embodiments of the invention provide means to solve the problem of rotation on the bearing itself when the post is inserted into the bone in the bearing.

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BRIEF DESCRIPTION OF THE DRAWING FIGURES

Figure 1 is a schematic sectional view illustrating the fracture fixation system of the invention. Figure 2 is a plan view thereof.

Figure 3 shows a part of the system of Figure 1 in a first stage of installation thereof.

Figure 4 shows the system in a completed installation stage.

Figure 5 is an elevation view of a bearing of the fracture fixation system.

Figure 5a shows a modification of the bearing of Figure 5.

Figure 5b shows another modification of the bearing of Figure 5.

Figure 6 is a flat plan view of the bearing.

Figure 7 is similar to Figure 4 and shows the forces developed when the bearing is expanded.

Figure 7a is similar to Figure 5 and shows a modification of the bearing thereof.

Figure 7b is similar to Figure 5 and shows another modification of the bearing thereof.

Figure 8 is an elevation view of another embodiment of the bearing.

Figure 9 is a bottom view of the bearing of Figure 8.

Figure 10 is a schematic perspective view of another embodiment of the bearing.

Figure 11 shows the bearing of Figure 8 in its initial state supported without pressure on the plate.

Figure 12 shows the bearing of Figure 8 after its rotation inside the plate.

Figure 13 shows a part of the plate in which the hole has been modified to prevent rotation of the bearing when the post is being installed.

Figure 14 shows the bearing installed in the hole in the plate of Figure 13.

Figure 15 is an elevational view of another embodiment of the bearing according to the invention.

Figure 16 is a sectional view taken along line 16-16 of Figure 15.

Figure 17 is an elevation view showing the bearing of Figure 15 installed in a hole in the plate.

Figure 18 is a sectional view taken along line 18-18 of Figure 17.

Figure 19 shows the bearing of Figure 17 in an angularly adjusted position.

Figure 20 is a sectional view taken on line 20-20 of Figure 19.

Figure 21 is an elevation view of another embodiment of the bearing.

Figure 22 is a cross-sectional view of the bearing of Figure 21 shown installed inside a hole in the plate.

Figure 23 shows the bearing of Figure 22 in a limited position slightly rotated inside the hole

of the plate.

Figure 24 is a side view of another embodiment of the bearing.

Figure 25 shows the embodiment of Figure 24 after it has been pretensioned.

Figure 26 shows the overlapping bearing contour shown in Figures 24 and 25.

Figure 27 shows the bearing of Figure 25 after it has been inserted into a bone fixation plate and before the insertion of a post into the bearing.

Figure 28 shows the bearing of Figure 27 after it has been inserted into the plate and after the insertion of a post in the bearing.

Figure 29 is a schematic elevational view of another embodiment according to the invention, in which the post has not yet been inserted into the bearing.

Figure 30 shows the embodiment of Figure 29, in which the post has been inserted into the bearing.

Figure 31 is a schematic elevation view of an embodiment not according to the invention, in which the bearing is free to rotate.

Figure 32 shows the embodiment of Figure 31, in which the bearing has been rotated and locked in place on the plate.

The invention will now be described with reference to the fixation of a fracture of the wrist radius using a fixation system that allows the fixation of the fracture and that holds the fracture and resists the forces that tend to cause displacement of the fracture. As will be apparent to persons skilled in the art, the invention is also applicable to other fractures, such as fractures of the fibula, internal ankle malleolus, distal end of the ulna, humerus and tibia.

Referring to Figures 1 and 2, they show, on an enlarged scale, the distal end portion of the radius 1 of the wrist in which a fracture 2 has formed near the distal end 3. Fracture 2 defines an unstable distal bone fragment 4 and a stable proximal bone fragment 5.

Fracture fixation 2 is achieved with a fracture fixation system 10 that includes a plate 11 having a proximal part 12 fixed to the stable proximal bone fragment 5 by bone screws 13. Bone screws 13 may have smooth heads or threaded heads that engage inside a threaded hole in the plate, the term screw being used to refer to either of the two types of fixing. The plate 11 has a distal part 14 having several spherical holes 15 in which fasteners 16 are attached which enter the unstable distal bone fragment 4 and are held therein. The fixing elements 16 can be in the form of pins, rods, wires or screws and in what follows they will be called posts. Posts 16 are supported

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within bearings 17 that are fastened in an adjustable manner in the holes 15 of the plate to allow the posts 16 to be placed at different angles 18 within the unstable fragment 4.

Figure 3 shows the post 16 in a partially inserted state in the bearing 17 and in the unstable fragment 4. Figure 4 shows the post in a fully inserted position, in which the bearing 17 is locked in the plate 11.

The bearing 17 has an outer surface 18 of spherical shape that fits into a respective hole 15 of the plate 11. The hole 15 has a correspondingly spherical shape like the outer surface of the bearing to give the bearing the ability to rotate within the hole. Accordingly, the bearing can be freely rotated in all directions within the hole 15 to adjust the angle at which the post 16 must be inserted in the fragment 4. The bearing 17 is provided with grooves (as will be explained in more detail forward) so that it is expandable to the outside and is locked in hole 15. When the post is fully inserted in the bearing, said bearing will be locked in hole 15.

To obtain the expandability of the bearing 17 to engage the bearing in the hole 15, the post has a threaded part 20 that meshes with a threaded bore 21 centrally located in the bearing that advances the post into the bearing. In one embodiment, the threaded part 20 of the post is oversized such that when said threaded part 20 of the post is advanced by threaded into the threaded bore of the bearing, it will produce a radial expansion of the bearing to securely engage said bearing in the inside the hole 15 of the plate 11. The threaded part 20 can be tapered along its entire length to produce increasing amounts of expansion as the post is advanced. Alternatively, the threaded portion may have a uniform diameter for most of its length such that a predetermined amount of expansion will occur. In either of the two embodiments, the threaded part 20 may have a conical area in the first thread fillets to make it easier to initiate the threading and to prevent tipping when the threaded part 20 is inserted into the threaded bore 21.

In another embodiment, a head 22 located at the end of the post is oversized with respect to the threaded bore 21, such that the head of the post causes expansion in the upper open end of the bearing when said head is inserted into the bearing. The head 22 allows the pole to be rotated to be advanced by threading into the bearing bore. The head 22 also limits the advance of the post inside the bearing. The post 16 may be shaped without a head 22 and a groove may be formed on the top of the post so that it can engage with it a tool to rotate the post and advance it into the bearing. In another embodiment in which the grooves of the bearing extend from the lower part of the bearing to the upper part partially or completely, the expansion mechanism may be formed by a reduced diameter of the lower end of the threaded bore 21 corresponding to a protrusion at the lower end of the threaded zone 20 of the post to cause expansion at the lower end of the bearing.

In Figures 3 and 4 the post is initially inserted through the open end of the bearing and the upper end of the post causes the bearing to expand when fully inserted. Since the expansion occurs mainly at the open end 23 of the bearing instead of the closed end 24, the outer surface 18 takes on a pear rather than a spherical shape when the expansion occurs. As will be shown later, this creates two contact zones at different levels of the hole 15 of the plate and improves resistance at times when forces are applied to the distal end of the post due to drift of the bone fragment 4.

In addition, the design of Figures 3 and 4 shows insertion into the bearing by the open end 23. The bearing could also be inverted, in which case the post will be inserted through the closed end 24 and the expansion will be generated by a conical thread at the lower end of the bearing bore.

Figures 5 and 6 illustrate a preferred embodiment of the invention in elevation and plan views, respectively. The bearing 17 is shaped as a body 30 in the form of a truncated sphere. To confer radial expandability to the bearing 17, a plurality of grooves 32 extend longitudinally along the length of the bearing, at equispaced circumferential intervals, from the upper edge 33 of the bearing to a position more than half the length of the bearing. bearing. Preferably, the groove extends ‘approximately * along three quarters of the bearing length. Although four slots have been shown in the embodiment of Figures 5 and 6, a greater or lesser number of them can be provided. The grooves 32 extend from the upper end 23 of the bearing to provide a means by which the bearing will be firmly locked in the plate as will be explained in greater detail below.

At the lower end of each groove 32, there is an enlargement to provide strain relief to prevent cracking at the bottom of the groove. The enlargement can take many forms, such as a horizontal cut to form a T-shaped enlargement. Preferably, the enlargement is in the form of an orifice 34 of diameter greater than the width of the groove that provides stress relief for the bearing. at the bottom of the groove to prevent cracking when the bearing expands. The grooves 32 define lever-shaped petals 35 circumferentially spaced around the bearing, the

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which act as cantilever beams, to experience opening as the post is advanced by threaded into the threaded bore 21 of the bearing. The stress relief holes 34 also increase the expandability of the lever-shaped petals 35. In a specific embodiment, the post has a diameter of 2.98 mm (0.117 ”), and the truncated bearing has a diameter of 4.19 mm (0.165”) and a height of 2.54 mm (0.100 ”). The bore of the bearing bore is substantially equal to the diameter of the post. The grooves have a width of 0.813 mm (0.032 ”) and a length of 1.85 mm (0.073”). The stress relief hole at the end of each slot has a diameter of 1.02 mm (0.040 ”). The bearing is made of stainless steel or titanium. The dimensions expressed in this document are only exemplary and will vary depending on the specific use.

Figure 7 shows the forces acting between the bearing 17 and the plate 11, which serve to lock the bearing in the plate, when the post is advanced by threading into the bore of the bearing. Specifically, as the post 16 is advanced by threading into the bearing 17, the upper ends 33 of the lever-shaped petals 35 expand outwardly into the hole 15. This causes the bearing to be pushed vertically. down trying to force it out of the bottom of the hole 15. When a load A is applied to the distal end of the post, the combination of the vertical displacement of the bearing inside the hole and the pear-shaped geometry of the expanded bearing produce a similar mechanism to a cam that joins the rotation of the bearing inside the hole and the generation of reaction forces F and T that produce a resistant force pair. Forces F and T are non-collinear and develop the pair of forces that securely and securely locks the bearing into the hole 15 of the plate. Conventional bearings that rely only on friction adjustment without the pair of forces may not adequately withstand the moments applied to the posts by migration of the bone fragments after fracture fixation. When a solid or fully divided spherical bearing is cylindrically expanded by a post, the main contact between the bearing and the surrounding hole occurs in the bearing's equator, which provides a limited frictional force generated from the contact area. relatively limited bearing against the hole to resist the applied moment. Since the friction contact area is relatively small, the friction forces are a fraction of the compressive forces F and T developed on the upper and lower surfaces as shown in Figure 7, and a relatively moment resistance is obtained. little. In the bearing of the present invention, the pair of forces developed by the two forces F and T, which are not collinear, provides a substantially greater resistance at times applied by loads from the unstable bone fragment into which the post has been inserted. .

By virtue of the shape of the force applied by the post when it is introduced into the hole (along a cylindrical front) and the asymmetric expansion of the bearing petals as cantilever beams, the contact between the bearing petals produces non-collinear compression forces. The resulting deformation of the metal between the bearing and the hole of the plate contributes to the non-collinearity of the forces. The absence of contact in the central or equatorial area of the bearing further favors the separation and non-collinearity of the compressed forces developed. As a result, when a moment is applied to the bearing due to the application of a moment to the post by the unstable bone fragment, to which the post is attached, a reliable pair of forces develops between the bearing and the bore of the plate to resist the moment applied to the post.

Figures 7a and 7b show two alternative embodiments that improve surface contact and resistance at times between the bearing and the hole 15 of the plate when the bearing expands cylindrically. To ensure that the contact area between the bearing and the hole 15 of the plate is not limited to a single equatorial plane, the hole of the plate may be shaped such that the central or equatorial area of the bearing does not make contact with the plate, whereby in the hole 15 of the plate contact will occur in two flat contact areas located at the upper end and at the lower end of the bearing, greatly increasing the surface contact area and the resistance to the applied moments. In Figure 7a the central or equatorial area 17a of the bearing is flattened along its entire perimeter, such that contact of the bearing is achieved with the bore 15 in contact areas 17b and 17c. In Figure 7b a central or equatorial zone 15a of the hole 15 is recessed, such that only upper and lower portions 15b of the hole 15 make contact with the bearing 17.

The systems of Figures 7a and 7b develop two contact rings above and below the equatorial bearing area, increasing the surface contact area and generating forces that are distributed unevenly across the thickness of the plate to resist moments

Although the sides of the grooves 32 have been shown straight and parallel within vertical planes, it is also possible to make the curved or angled grooves as shown in 32a in Figure 5a and make the grooves widen as shown in 32b in the Figure 5b The curved grooves 32a and widened 32b provide sharp angle shaped edges as shown in 36a and 36b, which tend to deform more as the post is installed inside the bearing and can be nailed into the hole wall of the plate to increase compression force and engagement of the upper part of the petals in the bearing hole.

Figures 8 and 9 show another embodiment of the bearing in elevation and plan views. The body 30 of the bearing 17 has a head 31 at its upper end. The head 31 has a hexagonal shape so that it can be

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engaged by a tool such as a wrench to prevent it from rotating on itself when the post is advanced by threading into the threaded bore 21 (see Figure 3) of the bearing. The head 31 is optional and the rotation of the bearing on itself can be prevented by friction with the wall of the hole 15 of the plate or by pins as will be explained later.

In Figures 8 and 9, two grooves 32A are shown that extend from the lower end 24 of the bearing upwardly along the length of the bearing and end in relief holes 34. The expansion mechanism is the same as in Figures 5 and 6 except that it is the lower ends of the petals 35 that are pushed outwardly when the bearing expands. A pair of forces similar to that shown in Figure 7 is produced.

Referring to Figure 10, there is another embodiment of the bearing designated by reference number 40. In this embodiment, the bearing is provided with two sets of grooves 32, 32A that alternately extend from opposite ends of the bearing . In this manner, the lever-shaped petals 35 extend from the upper and lower ends of the bearing and produce two pairs of forces in the contact areas that develop to engage the bearing in the hole 15 of the plate when the post is Insert inside the bore 21 of the bearing.

Figure 11 shows the bearing 17 of Figure 8 in its initially supported state without pressure on the plate 11 while Figure 12 shows that the bearing 17 after its rotation inside the plate 11 to its desired position.

Instead of using threads to engage the post in the bearing, the tapered end of the post can be made smooth and the post can be pushed axially into the bore of the bearing to produce expansion of the bearing.

Figures 13 and 14 illustrate a modification that employs means to prevent the bearing from rotating on itself within the hole 15 of the plate when the post 16 is threaded into the bore 21 of the bearing 17. In this regard, the plate it is provided with one or more grooves or grooves 50 extending from the hole 15. The bearing 17 is provided at its upper end with radially extending pins 51 that fit inside the grooves 50. After this, when the Post 16 is advanced into the bearing bore, the bearing will be firmly secured in the hole in the plate. Although two diametrically opposed grooves 50 and two 51 pins have been shown, only a single groove and a single pin may be necessary. It should be mentioned that, although this drawing shows the grooves and locking pins in the upper part of the bearing and plate, these can also be placed in the lower part of the bearing and plate without departing from the invention. The bearing may also be provided with a countersink 52 at the upper end of the borehole, such that when the post has been advanced to the end inside the borehole, the post head will be embedded in the bearing.

Another way of providing resistance of the bearing 17 to the rotation about itself within the hole 15 of the plate, when the post 16 has been advanced into the bore 21 of the bearing, is to provide micro-texture in the form of microsurks on the bearing surface. Microsurks also improve resistance to moments. In addition, microsurks can be provided on the surface of the hole 15.

Since the bearing and the orifice of the plate have corresponding spherical surfaces that fit closely to each other, there is a problem of installing the bearing in the orifice of the plate.

To avoid this problem, the grooves of the bearing can be made wide enough so that the bearing can be compressed to allow it to be inserted inside the hole of the plate and, after that, can resume its original spherical contour. The grooves give the flexibility of the bearing petals to allow insertion. This feature will be analyzed in more detail below with reference to Figures 24-27.

Another way of inserting the bearing into the hole of the plate is to initially form the hole with a large cylindrical diameter in its upper part to allow the insertion of the bearing. After that a crimping or crushing pressure is applied to the plate around the top of the hole, such that said hole is deformed and retains the bearing inside the hole while allowing the bearing to rotate freely.

Another additional way to install the bearing is to cool it in dry ice or liquid nitrogen and / or heat the plate, which will cause the bearing to shrink and the hole to expand allowing the bearing to be inserted into the hole. After the bearing and plate have returned to room temperature, the bearing will be retained with the allowed rotation inside the hole.

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Another problem to be solved is to prevent the bearing from rotating 180 ° and turning inside the hole preventing the correct installation of the post. To prevent this, the bearing is provided on one side of a small extension similar to pin 51 to prevent it from turning and turning.

The embodiment shown in Figures 15-20 is constructed to prevent the bearing from rotating about itself around a vertical axis during insertion of the post into the bearing bore and also to restrict the angular displacement of the bearing predominantly to a single flat.

Referring to Figures 15 and 16, there is shown a radial pin 60 extending outwardly from the surface of the bearing 61. The bearing 61 is similar to the bearings described above except that it is provided with a single groove 62 longitudinally extending along the entire length of the bearing to form a split bearing that can expand outwardly when the post (not shown) is inserted into hole 63 of bearing 61. The bearing can also be constructed with grooves. as shown in any of the preceding Figures or as a simple truncated spherical bearing with a single longitudinal groove as shown. The feature described in this embodiment is the means to prevent rotation on itself and restrict the angular displacement of the bearing. These means are composed of the pin 60 that engages in a groove 64 extending outwardly from the hole 65 of the plate 66 along the thickness of the plate. As seen in Figure 18, the pin system 60 and groove 64 form a type of cotter and keyway gear that limits the angular displacement around the vertical axis 67 of the bearing and allows the angular rotation of the bearing within the plane AA with capacity for a small amount of movement from side to side based on an oversizing of groove 64 with respect to pin 60 as seen in Figure 18.

Figures 19 and 20 show the bearing in an angularly rotated position inside the hole 65 of the plate 66 where the bearing has been turned to the side (clockwise) to the point allowed by the displacement of the pin 60 inside groove 64 oversized.

The use of a single pin as shown in Figures 15 and 16 has the disadvantage that the bearing tends to rotate around the pin as the post is inserted, generating a large cutting force through the pin. This can be solved by placing a second pin on the bearing and a second groove in the hole on the opposite side (not shown).

Figures 21 and 22 show a bearing 71 in accordance with a modified embodiment that limits the angular movement of the bearing 71 on the plate 11. The bearing 71 is provided with opposite flat faces 72 extending from the top of the bearing to the part lower, although any non-circular cross-section contour would perform an equivalent function. The plate 11 has a hole 73 with a shape that conforms to the outer surface of the bearing. Specifically, the hole 73 has flat faces 74 that are located in front of the flat faces 72 of the bearing and the rest of the hole surface is spherical and conforms to the bearing surface. Therefore, as shown in Figure 23, the angular rotation of the bearing is limited. The magnitude of angular movement is a function of the separation between the flat faces of the bearing and the hole. The embodiment also provides resistance to the rotation of the bearing on itself when the post is threaded into the bearing hole. In the embodiment illustrated in Figure 22, the bearing is free to rotate angularly within a vertical C-C plane.

Figures 24-28 show another embodiment designed to reduce stress and increase bearing resistance to fatigue failure and crack formation.

Referring to Figures 24-27 there is shown a truncated bearing 100 in which the groove 101 is wider at the lower end 102 than at the upper end 103. The groove ends in an area 104 of greater radius to provide stress relief against cracking in the top of the groove. The bearing has a spherical outer surface in its resting state and has a central threaded bore 105 for the insertion of a post with a threaded rod. The outer diameter of the bearing 100 is slightly larger than the diameter of the hole 201 of the plate 200.

Figure 25 shows the bearing after it has been compressed. The outer surface 102 of the bearing has been reduced in size allowing it to be inserted into the hole 201 of the plate 200. In addition, the compression has caused the central threaded bore 105 to narrow, with a width at the bottom of the hole smaller than on top. Finally, the compression has pretended a solid bearing bridge or zone 106 located above the groove 101 bending it upward causing a small compression on the lower surface of the bridge and traction on the upper surface of the bridge.

Figure 26 shows the non-tensioned bearing 100 superimposed on the pretensioned bearing 107 with the reduction of the cross-sectional diameter.

Figure 27 shows the post 108 before it is inserted into the prestressed bearing 107, which has been placed inside the hole 201 of the plate 200. The upper part of the post has a conical lower area 111 and a

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threaded upper zone 110 whose width coincides with the width of the upper part of the threaded bore 105 of the bearing 107. Prior to expansion, the bridge 106 located above the groove is pre-tensioned.

Figure 28 shows the expansion of the bearing 100 to its original shape as the post 108 is inserted. When the bearing is expanded the flexion of the bridge 106 located above the groove is similar to its original resting state, reducing the Tensions in this area when the bearing is expanded. This pre-stressed bearing design can be used with any of the other grooved bearing designs described above.

Figures 29 and 30 show another embodiment in which the bearing 107 is similar to that shown in Figures 24-28. The plate 11 in which the bearing is inserted is shown in Figures 29 and 30. The post 108 has a smooth cylindrical part 112 designed for insertion into a bone fragment (not shown). The cylindrical part 112 may also be threaded to increase engagement with the bone fragment. The post is provided with the threaded part 110 extending upwardly from the cylindrical part 112. The threaded part 110 is conical to facilitate entry into a widened end 114 located at the top of the threaded bore 113 of the bearing 107. The conical section 111 is fused with a cylindrical threaded portion 110, which engages by tapping into the bore 113 threaded bearing 107. On the upper part of the threaded upper part 110 of the post a head 109 is formed and said head 109 has a lower chamfered surface 116 that conforms to a chamfered surface 117 located at the upper end of the bore 113. When the post 108 is fully inserted in the bearing, the head of the post causes the open ends 33 of the petals 35 to expand and nail into the wall of the plate hole (not shown). This bearing expansion system can be used with any of the previously described embodiments in which the post is inserted through the open end of the bearing. The chamfered surface 116 can be formed with a conicity that has a small disparity with the taper of the chamfered surface 117 located on the top of the bearing 107 to form a Morse cone to engage the post in the bearing when fully inserted.

Referring to Figures 31 and 32, there is a plate 300 with a bearing 301 in the hole 302. In Figure 29, the bearing has the allowed rotation inside the hole 302 of the plate 300 and the post is not shown . The plate

300 is formed with a horizontal groove 303, which is partially cut horizontally on the plate to form an upper segment 304 of the plate, and a lower segment 305 of the plate, with a gap between the two. The segments 304, 305 of the plate are formed with respective aligned holes 306, 307. Hole 306 is smooth and hole 307 is threaded. In this embodiment, which is not part of the invention, the bearing

301 does not have to be divided or expandable. After the post (not shown) has been inserted inside the angularly fitted bearing and inside the associated bone fragment, the bearing 301 is locked in place by inserting the threaded fixing element 308 into the holes 306 and 307 to pinch and tighten the segments 304, 305 of the plate against the bearing 301 as shown in Figure 32. This will produce compression forces acting on the bearing in the upper right hemisphere and in the lower left hemisphere to produce forces that act unevenly on the bearing to develop resistance to the moments produced by the forces applied to the post.

Instead of being horizontal, slot 303 can be oblique or even vertical. Instead of partially traversing the plate, the groove can completely pass through the plate and the segments of the plate can be joined by hinges or screwed together. Instead of using a threaded fixing element 308 to compress the two segments of the plate, any connecting fixing element such as a clamp or a rivet can be used.

In addition, the bearing 301 may have one or more partial or complete grooves such that the two segments of the plate are compressed against the bearing, the bearing being compressed against the post to lock the post to the bearing.

Claims (11)

5 10 fifteen twenty 25 30 35 40 Four. Five fifty 55 60 1. A fixing system designed to hold bone pieces (4, 5) together, said fixing system comprising: a fixing element (16) designed to be attached to a first bone piece (4), a plate (11) comprising a spherical hole (15), and a bearing (17) to hold the fixing element (16) in an angular position adjusted within the hole (15) of the plate (11), said plate being designed to be held in a second bone piece (5) and to hold in this way the bony pieces (4, 5) with each other, said bearing (17) having an outer surface designed to rotate inside the hole (15) of said plate, said bearing (17) having a bore (21) inside from which the fixing element (16) is inserted and can be adjusted angularly by turning the bearing (17) into the hole (15) of the plate (11), in which the diameter of said hole decreases from a wider diameter in a plane that passes through an equatorial area of the hole to narrower diameters in respective planes along the upper and lower surfaces of the plate, and said bearing (17) is provided with a first end part having a spherical surface, a second end part having a spherical surface, and groove means (32) therein to allow radial expansion of the bearing when the element (16 ) of fixing is advanced within the bore (21) of the bearing (17), in which the groove means are constructed and placed in the bearing to hold the bearing in the plate, and in which said groove means comprise a plurality of grooves (32) extending from the first end part of the bearing partially along the length of the bearing to a position located more than half the length of the bearing, characterized in that, the grooves define lever-shaped petals (35) around said bearing, the fixing element comprising a part with a diameter that is greater than a diameter of a part of the hole comprising the lever-shaped petals (35), such that the advance of the bone fixation element (16) towards said part inside said borehole (21) causes the tips of the lever-shaped petals (35) to move outwardly to cause the spherical surface located in the first final part of the bearing (17) it rests against a spherical surface of the hole in a first side of the equatorial zone, while the spherical surface located in the second final part of the bearing (17) rests against a spherical surface of hole on the opposite side of the equatorial zone to develop a non-uniform distribution of force between the bearing and the plate that resists the moments applied to the migration fixation element of bone fragments when the fracture fixation system is holding the bone pieces (4, 5) together. 2. The fixing system of Claim 1, wherein the bearing (17) and the plate (11) are configured (15a, 17a) to prevent contact between the bearing and the plate in an equatorial area of the bearing when the bearing is expanded. 3. The fixing system of any one of claims 1 to 2, characterized in that said fixing element comprises a post having a bottom end portion designed to be fastened in said first bone piece (4), and a part (20) upper end that engages in the bore (21) of the bearing between the upper end of the post and the bore of the bearing to cause the bearing to expand and get stuck in the hole (15) when the upper end portion (22) of the post (16) is advanced within said bore (21) of said bearing and characterized in that said bearing is predominantly polyhedral with vertices defining the respective spherical surfaces of the first and second end portions of the bearing. 4. The fixing system of any one of claims 1 to 3, characterized in that the grooves (32) have terminal ends in the bearing that are enlarged (34) to provide stress relief and to increase the flexibility of said petals ( 35) lever-shaped 5. The fixing system of any one of claims 1 to 4, characterized in that said first end part of the bearing is the end end (23) thereof near an upper surface of the plate. 6. The fixing system of any one of claims 1 to 5, characterized in that said grooves (32) extend from opposite ends (23, 24) of the bearing (17) alternately to provide two sets of said petals ( 35) respectively attached to opposite ends (23, 24) of said bearing (16). 7. The fixing system of any one of claims 1 to 6, characterized in that said bore (21) and said upper end portion (22) of the fixing element (16) are threaded and characterized in that the part (20 ) upper end of the fixing element (16) is oversized with respect to the bore (21) of the bearing (16) to produce the expansion of the bearing (17) when the fixing element (16) is advanced by tapping into said bore (twenty-one). 5 10 fifteen twenty 25 8. The fixing system of any one of claims 1 to 7, characterized by a cotter system (60, 64) located between said bearing (17) and the hole (15) of the plate (11) to oppose the rotation relative latitudinal between them while allowing relative longitudinal rotation between them, and where said key system comprises a key (60) located on an element between the bearing or the hole (15) and a corresponding groove (64) for the key in the other element between the hole (15) or the bearing (17). 9. The fixing system of any one of claims 1 to 8, wherein the fixing element is a post, said post having an enlarged head part (20) that engages in the bore (21) of said bearing (17 ), said head part (20) and said bore (21) being configured to cause said bearing (17) to expand and be locked in said hole (15) when the head part (20) of the post is made advancing inside said bore (21) of the bearing, one of said bearing (61) or said hole (15) is provided with a groove (64) and the other of said bearing or said hole is provided with a pin (60), and where said groove (64) and said pin (60) are sized such that the pin (60) fits inside the groove (64) and prevents said bearing (61) from rotating on itself about an axis (67) vertical bearing (61) during insertion of said post in the bearing. 10. The fixing system of claim 9, characterized in that said groove (64) and said pin (60) are sized to restrict the angular movement of the bearing (61) inside the bore (15) in a single plane containing a A shaft of the hole. 11. The fixing system of claim 10, wherein said groove (64) is larger than said pin (60) to allow a limited range of motion from side to side of the bearing (61) within the bore (15 ) in addition to the angular movement of the bearing inside the hole in the only plane that contains the axis of the hole.